What is the best way to change the rack of a node?

I have tried the following: Killed the datanode process. Changed the rackmap
file so the node && and ip address entry reflect the new rack and I do a
'-refreshNodes'. Restarted the datanode.  But it seems the datanode is keep
getting register to the old rack.

--
--- Get your facts first, then you can distort them as you please.--

IMHO, any effort spent trying to squeeze a gain from rack awareness is a
waste of time. High speed networks & Moore's Law pretty much make the
notion obsolete faster than any benefit (if there is one) can catch up to.

Not an answer to your question though. I realize that.

> What is the best way to change the rack of a node?
>
> I have tried the following: Killed the datanode process. Changed the
> rackmap
> file so the node && and ip address entry reflect the new rack and I do a
> '-refreshNodes'. Restarted the datanode.  But it seems the datanode is
> keep
> getting register to the old rack.
>
> --
> --- Get your facts first, then you can distort them as you please.--
>

Darren, people don't necessarily make things rack aware for performance.  Consider if you have a rack of datanodes and all your block replicas  on nodes in that rack. If you have a switch, power strip failure you would be down.  You are also able to provision in data centers two circuits so by placing racks on different circuits reduces your chances of having downtime if their is a power failure.  The power case of course you can also handle by buying more expensive hw that has dual power supplies straddling the two circuits.

C
On Mar 26, 2011, at 2:00 PM, <[EMAIL PROTECTED]> wrote:

> IMHO, any effort spent trying to squeeze a gain from rack awareness is a
> waste of time. High speed networks & Moore's Law pretty much make the
> notion obsolete faster than any benefit (if there is one) can catch up to.
>
> Not an answer to your question though. I realize that.
>
>> What is the best way to change the rack of a node?
>>
>> I have tried the following: Killed the datanode process. Changed the
>> rackmap
>> file so the node && and ip address entry reflect the new rack and I do a
>> '-refreshNodes'. Restarted the datanode.  But it seems the datanode is
>> keep
>> getting register to the old rack.
>>
>> --
>> --- Get your facts first, then you can distort them as you please.--
>>
>

I think that the namenode remembers the rack.  Restarting the datanode
doesn't make it forget.

On Sat, Mar 26, 2011 at 7:34 AM, Rita <[EMAIL PROTECTED]> wrote:

> What is the best way to change the rack of a node?
>
> I have tried the following: Killed the datanode process. Changed the
> rackmap
> file so the node && and ip address entry reflect the new rack and I do a
> '-refreshNodes'. Restarted the datanode.  But it seems the datanode is keep
> getting register to the old rack.
>
> --
> --- Get your facts first, then you can distort them as you please.--
>

On Mar 26, 2011, at 3:50 PM, Ted Dunning wrote:

> I think that the namenode remembers the rack.  Restarting the datanode
> doesn't make it forget.

Correct.

https://issues.apache.org/jira/browse/HDFS-870

Thanks Allen.

I really hope this gets addressed. Leaving it in cache can become
dangerous.
On Sat, Mar 26, 2011 at 7:49 PM, Allen Wittenauer
<[EMAIL PROTECTED]>wrote:

>
> On Mar 26, 2011, at 3:50 PM, Ted Dunning wrote:
>
> > I think that the namenode remembers the rack.  Restarting the datanode
> > doesn't make it forget.
>
> Correct.
>
> https://issues.apache.org/jira/browse/HDFS-870
>
>
--
--- Get your facts first, then you can distort them as you please.--

This may be weird, but I could have sworn that the script is called repeatedly.
One simple test would be to change the rack aware script and print a message out when the script is called.
Then change the script and see if it catches the change without restarting the cluster.

-Mike
> From: [EMAIL PROTECTED]
> Date: Sat, 26 Mar 2011 15:50:58 -0700
> Subject: Re: changing node's rack
> To: [EMAIL PROTECTED]
> CC: [EMAIL PROTECTED]
>
> I think that the namenode remembers the rack.  Restarting the datanode
> doesn't make it forget.
>
> On Sat, Mar 26, 2011 at 7:34 AM, Rita <[EMAIL PROTECTED]> wrote:
>
> > What is the best way to change the rack of a node?
> >
> > I have tried the following: Killed the datanode process. Changed the
> > rackmap
> > file so the node && and ip address entry reflect the new rack and I do a
> > '-refreshNodes'. Restarted the datanode.  But it seems the datanode is keep
> > getting register to the old rack.
> >
> > --
> > --- Get your facts first, then you can distort them as you please.--
> >
     

I think I tried this. I have a data file which has the map, ip address:rack,
hostname:rack. I changed that and did a refreshNodes. Is this what you mean?
Or something else? I would be more than happy to test it.

On Mon, Mar 28, 2011 at 4:15 PM, Michael Segel <[EMAIL PROTECTED]>wrote:

>  This may be weird, but I could have sworn that the script is called
> repeatedly.
> One simple test would be to change the rack aware script and print a
> message out when the script is called.
> Then change the script and see if it catches the change without restarting
> the cluster.
>
> -Mike
>
>
> > From: [EMAIL PROTECTED]
> > Date: Sat, 26 Mar 2011 15:50:58 -0700
> > Subject: Re: changing node's rack
> > To: [EMAIL PROTECTED]
> > CC: [EMAIL PROTECTED]
>
> >
> > I think that the namenode remembers the rack. Restarting the datanode
> > doesn't make it forget.
> >
> > On Sat, Mar 26, 2011 at 7:34 AM, Rita <[EMAIL PROTECTED]> wrote:
> >
> > > What is the best way to change the rack of a node?
> > >
> > > I have tried the following: Killed the datanode process. Changed the
> > > rackmap
> > > file so the node && and ip address entry reflect the new rack and I do
> a
> > > '-refreshNodes'. Restarted the datanode. But it seems the datanode is
> keep
> > > getting register to the old rack.
> > >
> > > --
> > > --- Get your facts first, then you can distort them as you please.--
> > >
>

--
--- Get your facts first, then you can distort them as you please.--